This application claims priority under 35 U.S.C. xc2xa7119 to Patent Application Serial No. MI 2002A 000787 filed in Italy on Apr. 12, 2002, the entire content of which is hereby incorporated by reference.
The present invention relates to a towing device to be used with sorting machines, for example of the xe2x80x9ccross beltxe2x80x9d type, for carriage towing. These machines can exhibit different layouts (linear, carousel-like, L-shaped, etc.) and they consist of a train of carriages moving along a sorting path, from item input stations to devices for collecting sorted items. See, for example, U.S. Pat. No. 5,803,230, the disclosure of which is incorporated herein by reference.
The term xe2x80x9cCross Beltxe2x80x9d indicates that the sorting unit with which the carriage is equipped, is a small conveyor belt capable of moving independently, by an electric motor, in the two directions orthogonal to the running direction of the sorting machine.
According to a known method, carriages are propelled or towed by fixed driving wheels which, by friction, engage with a plate integral with said carriages. In the practice, each carriage is provided with a blade or plate arranged in vertical and longitudinal position below the same carriage and integral with it. Carriages are reciprocally interconnected by an articulated joint that allows them to cover curved and/or variable slope portions. The blades below them are fitted so as to obtain an optimum alignment.
Since the blades are not perfectly aligned, the wheels must be capable of following the small side movements of the blades, in turn making small movements transversely of their respective axes.
Such small movements, following an increase in speed of the sorting machines, are quite sudden and since they tend to make the wheels bounce, even though for a very short time, the wheels may slide, with a resulting loss of thrust to the disadvantage of the regularity of motion, but above all, with a resulting decrease of the life of the friction gaskets which cover the driving wheels. This also causes a certain noise.
The present invention intends to strongly reduce such disadvantages through a drafting device that, thanks to the low inertia of the moving equipment, is capable of promptly following the side movements of the blades. In particular, the invention relates to an apparatus for propelling a track-mounted carriage that has a vertically projecting blade. The apparatus comprises a pair of driving wheels forming therebetween a nip adapted to receive the blade, the wheels being driven by a motor arrangement and being movable toward and away from the nip independently of the motor arrangement in response to blade misalignments.